Optimization Of Soybean Paste Fermentation Process Based On Soy Sauce Residue Utilization

Soy sauce residue,refers to the solid residue produced by brewing soy sauce.The output of soy sauce is huge in China,so is the annual output of soy sauce residue.The soy sauce residue is still rich in protein,fat and other nutrients which have not been used.But its high moisture and salt content,transport difficulty,decay and deterioration easily,is easy to cause environmental pollution without timely treatment.With the strategy of cleaner production,the reuse of soy sauce residue is urgently needed.In this paper,soy sauce residue was used to replace soybean and flour partly,and a new type of Monascus soybean paste was prepared by combining Aspergillus oryzae and Monascus separated or compound starter-making and fermentation technology.The soybean processing by-products were returned to production as secondary raw materials,which provided a new way to solve the problem of high-value reuse of soy sauce residue resources.The main contents and results are as follows:(1)According to the sensory and physicochemical indexes of soybean paste with different soy sauce residue content(1%,3%,5%,7%,9%)and without,the effects of soy sauce residue on soybean paste were studied.It showed advantages in volatile flavor substances and comprehensive sensory evaluation.(2)The starter-making time was determined by the activity of neutral protease and glucoamylase.The results showed that the activity reached the highest when inoculated solely with Aspergillus oryzae at the fermentation time of 48 h,which were 1033.27 U/g and 1605.34 U/g,respectively.The conditions of soy sauce residue,Monascus powder,salt water concentration and addition in soybean paste inoculated with Aspergillus oryzae alone were optimized by single factor and orthogonal experiment according to the sensory and amino nitrogen content.The results showed that the addition of 90%salt water,7%soy sauce residue,16°Bé salt water and 1.5%Monascus respectively made the best.(3)Monascus and Aspergillus oryzae were used to make koji separately,and mixed inoculation was used to make mixed-strain koji.The activity of neutral protease and glucoamylase was the highest when the inoculation amount of Monascus was 1.5%,Aspergillus oryzae 0.04%and the time was 72 h.Amino acid nitrogen and sensory score were used as indicators to determine the amount of soy sauce residue.The results showed that the addition of 10%soy sauce residue could reduce the content of amino acid nitrogen,but at the same time,the sensory of soybean paste could be improved.(4)By measuring the color,texture,sensory,physicochemical and flavor substances of soybean paste,the quality indexes were compared and analyzed.The results showed that soy sauce residue could significantly improve the color and sensory quality of soybean paste,maintain good physicochemical indexes and enrich flavor substances.In addition,the production cost of 5.48%and 8.4%can be reduced by adding soy sauce residue.